Effects of ultrasonication power and treatment time on the structural, physicochemical, functional, thermal, and rheological properties of sorghum starch

Sorghum starch has considerable potential for food applications; however, its limited functionality restricts its broader industrial utilization. Although ultrasonication has been widely used to modify starches from various botanical sources, information regarding the influence of different ultrasound power levels and treatment durations on sorghum starch remains limited. Therefore, this study investigated ultrasonication as a green and nonchemical modification technique to improve the physicochemical, structural, thermal, and rheological properties of sorghum starch. Ultrasonication was applied at a frequency of 20 kHz and a maximum output power of 600 W, using power levels of 20%, 40%, and 60% for 20 and 30 min. The results revealed significant (p < 0.05) improvements in starch functionality, with the highest water absorption capacity (2.37 g/g) and oil absorption capacity (4.33 g/g) observed at 60% power for 30 min. The apparent amylose content significantly (p < 0.05) increased to 33.66%, whereas the enhanced paste clarity, swelling power, and solubility indicated increased molecular disruption and water interaction. Ultrasonication reduced the peak viscosity from 1227 to 777 cP and significantly decreased the breakdown and setback viscosities, suggesting improved paste stability and a lower tendency toward retrogradation. Furthermore, reductions in the storage modulus (G′) and loss modulus (G″) indicated disruption of molecular associations and modification of viscoelastic behavior. Overall, ultrasonication effectively improved the functional and rheological properties of sorghum starch, highlighting its potential as an eco-friendly modification technique for food applications requiring enhanced hydration characteristics and improved paste stability.